Experimental study of the scour regimes downstream of an apron for intermediate tailwater depths

Local scour due to 2-D submerged horizontal jets is a well-known topic of hydraulic research. When the jet is directly injected on the erodible bed and the tailwater depth is either "deep" or "shallow", the equilibrium state characteristics of the scoured bed profile are mainly a function of the densimetric Fronde number. If the submergence is between these two extremes, for fixed Froude number, three different scour regimes are possible, depending on the jet mainstream position. This paper integrates previous work by the Authors concerning the experimental description of the three mentioned regimes, in presence of a protection apron. The results of the investigation are also intended as a dataset to validate numerical models able to simulate the interaction between free-surface flows and non-cohesive granular beds.